The vast majority of leukocyte antigens are destroyed by routine processing to paraffin blocks. As a result, the use of monoclonal antibodies (MAbs) to identify cell lineage, cell differentiation and cell subset populations have been restricted to fresh frozen tissue sections. In many instances, however, fresh frozen tissue sections may not be available for analysis. It is desirable, therefore, to find and identify MAbs that will react with leukocyte antigens in routinely processed, paraffin-embedded tissues.
Currently on the market are several monoclonal antibodies purportedly constructed to satisfy this desire. Among these antibodies are: Clonab MT1, MT2, MB1 and MB2 (available from BioTest, Inc.); LN1, LN2 and LN3 (available from Techniclone International); and Dako LC and UCHL-1 (available from Dako Corp.). Descriptions of each group of monoclonal antibodies have been reported in: Poppema et al., Monoclonal Antibodies (MT1, MT2, MB1, MB2,) Reactive with Leukocyte Subsets in Paraffin-Embedded Tissue Sections, Am. J. Pathol., 127:418-429 (1987); Epstein et al., Two New Monoclonal Antibodies (LN-1, LN-2) Reactive in B5 Formalin-Fixed, Paraffin-Embedded Tissues with Follicular Center and Mantle Zone Human B Lymphocytes and Derived Tumors, J. Immunol., 133:1028-1036 (1984); and Norton et al., Momoclonal Antibody (UCHL1) that Recognizes Normal and Neoplastic T Cells in Routinely Fixed Tissues, J. Clin. Pathol., 39:399-405 (1986).
Although these MAbs function in other than frozen tissue sections, the antigens they react with are of limited use both in terms of their distribution and specificity. A number of these MAbs will cross-react between T and B cell lines, for example. Thus, the usefulness of these MAbs is somewhat limited.
It would be desirable, therefore, to find an antigen that is distributed on T cell malignancies but not on B cell malignancies. This is of clinical importance because T cell malignancies behave more aggressively than B cell malignancies, and thus, require more aggressive treatment.
Similarly, the diagnosis of Hodgkin's from non-Hodgkin's lymphomas is important because of the vast prognostic and therapeutic differences between the diagnostic alternatives. For determination of Hodgkin's versus non-Hodgkin's lymphomas, therefore, it would be useful to have a monoclonal antibody that would identify an antigen that discriminates between Hodgkin's and non-Hodgkin's lymphomas.
Leu 22 is antigen of approximately 100 kD that is found on normal and malignant T cells, peripheral blood monocytes and a subpopulation of normal B cells and tissue macrophages. It is conserved on non-Hodgkin's lymphomas of T cell origin but is not found on Reed-Sternberg cells in Hodgkin's disease. Thus, the Leu 22 antigen has many of the characteristics desired.